WO 2008/076720 discloses an optical level detection sensor for a liquid overfill prevention system to be used in an overfill prevention system for liquid fuels.
This known optical liquid level detection sensor comprises a light source for emitting a light beam, a cone shaped transparent prism element forming liquid contact surface, and a light detector. The light source and the light detector are arranged in a longitudinal housing. The light source is arranged to emit a light beam towards the liquid contact surface, which liquid contact surface reflects or transmits the light beam in dependence of liquid being present on the liquid contact surface. The light detector is arranged to receive the light beam after reflection on the liquid contact surface. When the light beam is transmitted through the liquid contact surface due to the presence of liquid on this contact surface, the light beam will no longer reach the light detector. As a result, the presence of liquid on the liquid contact surface may be determined in dependence of the amount of light received by the light detector.
In the construction of the level sensor of WO 2008/076720, the prism is press-fitted into a metal retention ring and the metal retention ring is press-fitted into the probe body to obtain a sealing engagement between the prism and the probe body.
A drawback of such construction is that the press-fitted connection between the metal retention ring and the prism and between the metal retention ring and the probe body is relatively difficult to assemble. As a result, there is a risk that the sensor is not properly sealed, and that liquid can enter the interior of the sensor.
A further drawback of this construction is that the press-fitted connection cannot be taken apart without damage to the prism, metal retention ring and/or probe body.